Composition for inhibiting corrosion



ug- 22 1967 R. L. LlTTLl-:R ETAL 3,337,472

COMPOSITION FOR INHIBITING CORROSION Filed April 8, 1966 IN VENTORS 9055/97- 44 0725/? United States Patent O COMPOSITION FOR INHIBITING CORROSION Robert L. Littler, Bay City, Tex., and Glenn A. Marsh and Edward Schaschl, Fullerton, Calif., assignors to Union Oil Company of California, Los Angeles, Calif.,

a corporation of California Filed Apr. 8, 1966, Ser. No. 541,376 4 Claims. (Cl. 252-392) This application is a continuation-in-part of application Serial No. 400,269, led Sept. 29, 1964, which is in turn a continuation-impart of application Ser. No. 243,657, liled Dec. 10, 1962, both applications abandoned.

This invention relates to a corrosion inhibiting composition and more particularly to the inhibition of corrosion of ferrous metals contacted by petroleum fractions.

Petroleum fractions such as gasoline, diesel fuel, and naphthas are often seriously corrosive to ferrous metal structures such as storage tanks, pipelines, earth well bore tubing and casing, processing equipment, etc. Corrosion of such structures is inhibited by incorporating in the petroleum fraction a small amount of a corrosion inhibitor before entry of the fraction into the metal structure. The inhibitor selected, aside from having no deleterious effect upon the petroleum fraction itself or its use, must, in the amount in which it is used, reduce corrosion in the equipment to a tolerable level. Hence, the cost of the inhibitor, considered in the light of the amount in which it is -used per volume of petroleum fraction, should be as low as possible.

Numerous excellent corrosion inhibitors are known, which, when used in petroleum fractions, will reduce the corrosion of ferrous structures to a very low level. Unfortunately, the cost of such inhibitors is very great. Other, less expensive inhibitors, are less effective per unit of inhibitor employed, and therefore must be used in undesirably great amounts.

It is an object of this invention to provide a new inhibitor composition which provides excellent corrosion protection at reasonable cost.

Another object of this invention is to providean im proved method for inhibiting the corrosion of various types of ferrous metal equipment.

The ligure is a graph prepared from corrosion rates experimentally determined using individual components of the composition forming the subject matter of'this invention.

The objects of this invention are accomplished by incorporating in the petroleum fraction which is to be stored or transported by the equipment and which is corrosive to ferrous metals, a small amount, in the range of about 5 to 50 parts per million, and preferably about 5 to 15 parts per million of the corrosion-inhibiting composition of this invention which comprises a combination of at least two of the following components: (1) an acyl derivative of N-alkyl amino acetic acid, (2) a substituted imidazoline, and (3) a fatty acid addition salt of a diamine.

The acyl derivative of N-alkyl amino acetic acid has the formula:

Rl-fliN-OHZ-COOH in which R1 is an aliphatic radical of about 10 to 24 carbon atoms, and R2 is hydrogen or an alkyl radical of l to about 6 carbon atoms. Preferred compounds are those in which R2 is a methyl group, that is, those compounds that are derivatives of methylamino acetic acid. More especially preferred are compounds wherein the R1 group is a fatty acid residue and is derived from tall oil or oleic acid.

Since it is difcult and expensive to obtain compounds of the above formula in pure form, this invention contemplates the use 0f mixtures of such compounds. The composition of such mixtures may range from those in which the fatty acid residue (R1) is 95% C12to compounds in which of the fatty acid residue is derived from C18 or higher acids. The following specific compounds are illustrative:

(N-oleoyl) methylamino acetic acid (N-palmitoleoyl) methylamino acetic acid (N-dodecylenoyl) methylamino cetic acid (N-ricinoleoyl) methylamino acetic acid (N-dicylenoyl) methylamino acetic acid (N-linolenoyl) methylamino acetic acid (N-lauroyl) methylamino acetic acid (N-palmitoyl) methylamino acetic acid (N-stearyl) methylamino acetic acid Other compounds are the corresponding acids wherein the R2 radical is hydrogen or an ethyl, propyl, butyl, amyl, or hexyl radical.

The substituted imidazoline has the formula:

/N-CHr n-o/ N-CH2 1l. in which R3 is an aliphatic or cycloaliphatic radical of about 10 to 32 carbon atoms and R4 is an alkyl, a hydroxy-substituted alkyl, or an amino-substituted alkyl radical of about 1 to 6 carbon atoms. IPreferred compounds are those where R4 is Z-hydroxyethyl and R3 is either heptadeoenyl or the residue from tall oil fatty acids. Other suitable compounds are:

2-heptadecenyl-1-(4-hydroxybutylimidazoline) 2dodecyll (S-hydroxypentylimidazoline) 2- 3 -cyclohexylpropyD -1- (2-hydroxyethylimidazoline) 2-dodecylcycloheXyl-1- (2-hydroxyethylimidazoline) 2-octadecyl-1- (3 -hydroxypropylimidazoline) 2-hept adecenyll-methylimid azoline 2-heptadecenyl-l -ethylimid azoline 2-heptadecenyll -butylimidazoline 2-dodecyl- 1 -pentylimid azoline 2- (3 cyclohexylpropyl) l-methylimidazoline 2-dodecylcycloheXyl-l -ethylimidazoline 2octadecyl l -propylimidazoline 2-heptadecenyl-1( Z-aminoethylimidazoline) 2tridecyl 1 (Z-aminoethylimidazoline) 2pentadecyl1-(Z-aminoethylimidazoline) The fatty acid salt of a diamine has the formula:

in which R5 and R6 are aliphatic radicals of about 10 to 32 carbon atoms per radical and n is an integer from l to about 4. Preferred compounds are those in which n is 3, R5 -is either oleyl or is derived from tallow acids and consists mainly of C16 and C18 normal, saturated hydrocarbon chains and C18 monounsaturated chains, and R6 is oleyl or is derived from tall oil acids free of resin acids. Examples of other suitable compounds are octadecenylaminopropyl ammonium oleate, octadecenylaminobutyl ammonium oleate, octadecenylaminoethyl ammonium oleate, octadecenylaminopropyl ammonium stearate, octadecenylaminopropyl ammonium palmitate, octadecenylaminoethyl ammonium laurate, hexadecenylaminopropyl ammonium oleate, dodecenylaminopropyl ammonium oleate, and mixtures of the foregoing compounds.

The effectiveness of the compositions of this invention is demonstrated by experimental tests which show the corrosion rates for metal specimens when protected by the compositions of the invention and when protected by the individual constituents of the composition when used alone. A mild steel coupon, initially 5 mils thick, is etched for 15 seconds in 6 N hydrochloric acid containing 1% iron chloride. Then the coupon is prerusted by alternate dipping into a rusting solution for 10 seconds, with intermittent drying, for 4 complete cycles. The rusting solution is an aqueous 3% sodium chloride, 1% iron 4 Amine 2 heptadecenyl l-(Z-hydroxyethylimidazoline). Amine T-2 (tail oil-derived)-1-(2-hydroxyethylimidazoline).

t t D TD o-[R-lI-oH-oriz-oHl-llnpqourrso 0].-

in which R is derived from tallow acids and consists mainly of C16 and C18 normal, saturated chains and C18 mono-unsaturated chains.

PR-Z-Same as DTDO except R is an oleyl group and the acid radical is derived from tall oil acids free of chloride solution. A uniform yellow-orange rust that resin acids.

TABLE I Components Concentration l and Individual Corrosion Rates Percent Protection 2 of Indi- Percent Protection vidual Components Cost of Corrosion Treat- Rate of ment,3 Corro- Corro- Corro- Combined Sum o Com- S per 4 Component 1 sion Composion Composion Components Compo- Compo- Compo- Indibined 1b.

Rate, nent 2 Rate, nent 3 Rate, nent 1 nent 2 nent 3 vidual Compo- Treatyin./hr. pin/hr. pin/hr. Components ment nents Sarkosyl T Amine T DTDO 0.5 lb. 3. 9 0. 51h. 4. 4 3. 0 lb. 3. 5 0. 08 29 20 26 75 99 1. 92

Sarkosyl T Amine T IER-2 0.5 lb. 3.9 0. 5 lb. 4. 4 3.0 lb. 3. 5 0.07 29 20 26 75 99 1. 92

Sarkosyl O Amine O PR-2 0.5 lb. 3. 9 0. 5 lb. 4. 4 3. 0 lb. 3. 5 0. 05 29 20 26 75 99 1. 95

Sarkosyl T Amine T 2.0 lb. 2. 3 2. 0 lb. 4.6 0.13 58 16 74 98 2.86

Sarkosyl O P R-2 1.0 lb. 3. 3 3. 0 lb. 3. 5 0.15 40 26 66 97 2. 20

Sarkosyl O Amine O 1.0 lb. 3. 3 3. 01h. 4. 7 0. 05 40 15 55 99 2. 50

Sarkosyl O P R-2 2.0 lb. 2. 3 2. 01h. 4. 6 0.25 58 16 74 95 2.80

Amine O PR-2 2. 0 lb. 4. 6 2. 0 lb. 4. 6 0.75 16 16 32 86 1.76

Sarkosyl O Amine O 2.0 lb. 2. 3 2.0 lb. 4. 6 0.20 58 16 74 96 3. 00

1 In pounds per thousand barrels of isooctane.

penetrates to 10 to 15 microinches is produced on the coupon.

The prerusted coupon is inserted in a l-quart narrowmouthed square bottle containing 450 milliliters of isooctane and 450 milliliters of aerated 3% brine. The coupon is kept in the hydrocarbon phase (which contains the inhibitor to be tested) for a soaking period of 1 hour. After this the bottle is oscillated at a `rate of 2 cycles per minute to immerse the coupon alternately in the 2 phases. Metal loss measurements are made throughout the test by electronic means that do not interfere with the continuity of the test. The average slope of the corrosion curve for duplicate runs is taken as the corrosion rate. Since the curves are not precisely linear, the slope is chosen between fixed time limits of and 60 hours after the start of the test. A good inhibitor permits only a low corrosion rate-and in some cases no corrosion-while a poor inhibitor or too little inhibitor permits a rate approaching or perhaps exceeding the blank (no inhibitor) rate of metal loss per hour.

Example The results of experiments performed according to the above procedure `are set forth in Table I. Blanks were run to determine corrosion rate in the absence of any inhibitor. This was found to be 5.50 microinches per hour. In Table I trade names, dened as follows, are used for purpose of brevity.

Sarkosyl O(Noleoyl) methylamino acetic acid. Sarkosyl T--N-(tall oil-derived acyl) methylamino acetic acid.

3Cost based on less than 10 drum quantities: Sarkosyl O, 1.00/lb.; Sarkosyl T, 0.95/1b.; Amine O, 0.50/lb.; Amine T, OAS/1b. DTDO, 0.40/1b. 13R-2, 0.40/1b.

In evaluating the results of the foregoing experiments, it should be borne in mind that while the acyl derivatives of methylamino acetic acid tested prove to be extremely effective as corrosion inhibitors when used alone, these materials are too costly at the levels required to provide adequate corrosion protection. The imidazoline and fatty acid amine salt additives are very much less expensive, but these materials, by themselves, do not provide an adequate level of corrosion protection unless used in large amounts. It is seen, nevertheless, that lthe combination of a very small amount of the derivative of N-alkylamino acetic acid, together with an equal amount of the imidazoline and a greater amount of the fatty acid salt (the least expensive additive), provides, at a reasonable total dosage level of 4 pounds per thousand barrels, a very adequate level of corrosion protection at low cost.

The graphs shown in the drawing were prepared by experimentally `determining corrosion rates, in accordance with the method described above, using individual components of the claimed composition in different amounts. For example, corrosion rate in microinches per hour was determined for both Amine T and Amine O at doses of 0.5, 4.0 and 6.0 pounds per 1,000 barrels of isooctane. From the curve it is apparent that even at the 6 pound dosage, Amine T and Amine O were not particularly effective. On the other hand, while Sarkosyl O and T are not very effective at 0.5 pound dosage, they give substantially complete protection at 4.0 dosage. DTDO and PR-Z appear to have negative action at 0.5 pound dosage between 6 and 7 pounds.

Best results are obtained by mixing together at least one compound of each of the three components; however, substantially improved corrosion at lower cost can be obtained by mixing together two components in the amounts of about l to 3 parts of one -with 3 to 1 parts of the other. For example, as shown in Table I, Sarkosyl O land Amine T give lalmost complete protection at a lower cost than Sarkosyl T alone. The same is true of the combination of Sarkosyl O and PR-2. Amine O together with PR-2 give a substantial measure of protection at a low cost. But the combination of the three components consistently 4gives the greatest protection against corrosion at the lowest cost. Regardless of whether two or three components are mixed together, each Icomponent should be present in an amount not less than about 10 percent by weight of the mixture, i.e., a range of about percent to about 90 percent by weight, and where two components are used, each should be present in an amount of at least 25 percent by weight. In order to reduce the cost of inhibiting, the acyl `derivative of N-alkyl amino acetic -acid should be kept as low las possible consistent with adequate corrosion protection. Proponi-ons of about 0.8 to 1.2 parts by weight for each of the Naalkyl amino acetic acid derivative and the imidazoline and about 5.5 to 6.5 part-s by weight for the diamine salt have been found to give particularly good results.

Although the compounds and proportions shown in the above example have been found to give optimum results, the synergistic eifect of applicants compositions is not limited to the specific compounds :and proportions set forth therein. Compositions comprising a wide variety of compounds, as set forth in the above generic formulae, and proportions as set forth in the preceding paragraph (at least about l0 percent of each component) will exhibit synergism comparable to that shown in the examples.

We claim:

1. A Icorrosion inhibiting composition consisting of the following three components:

(I) About 0.5 part by weight of an acyl derivative of N-alkyl amino acetic acid of the formula:

o CH3 Rl-(Ii-llI-CHa-C O OH in which R1 is selected from the group consisting of Naoleoyl :and N-(tall oil-derived acyl); (II) About 0.5 part by weight of an imidazoline tof the formula:

/N-CHa R-o/ \N-CH2 CzHsOH in which R3 selected from the group consisting of 2-heptade'cenyl and 2-(tall oil-derived); and (III) About 3 parts by weight of a fatty acid salt of a diamine of the formula:

H H {R5-1%I-( CH2) s-Ill H]++[R5CO Oh' in which R5 is lselected from the group consisting of (a) Tallow derived acids of mainly C16 and C18 normal, saturated chains and C18 monoJunsaturated chains, and (b) an oleoyl group; and R6 is selected from the group consisting of: (a) C17H33 and (b) tall oil derived acids free of resin acids.

2. A corrosion inhibiting composition consisting of:

(a) about one part by weight of a compound selected from the group consisting of an N-(oleoyl) methyl amino `acetic acid, and N-(tall oil-derived .'acyl) methyl amino acetic acid; and

(b) about three parts by weight of a fatty acid salt of a diamine of the formula:

where R5 is selected from the group consisting of oleoyl and tallow acids having mainly C16 land C18 normal saturated hydrocarbon chains and C18 mono unsaturated hydrocarbon chains; and R6 is selected from the group consisting of tall oil acids free of resin acids 'and C17H33.

3. A corrosion inhibiting composition 'consisting of:

(a) about one part by weight of a compound from the group consisting of: an N-(oleoyl) methyl amino acetic acid; :and N-(tall oil-derived acyl) Amethyl amino acetic; and

(b) about three parts by weight of fa compound from the group consisting of: 2heptadecenyl1(2l1y rlroxyethyDimid-azoline; and 2-(tall oil-derived)l (Z-hydroxyethyl) imidazoline.

4. A corrosion inhibiting composition consisting of about equal parts by weight of (a) Z-heptadecenyl-1-(2-hydroxyethyl)imidazoline; and

(b) a fatty acid salt of a diamine of the formula:

t t [R5-1T -(CH2) a-l BIF-*[RO O O12- were R5 is an oleoyl group and R6 is derived from tall oil acids free of resin acids.

References Cited UNITED STATES PATENTS 2,468,163 4/ 1949 Blair et tal. 252-855 2,736,658 2/ 1956 Pjohl 44-66 X 2,790,779 4/ 1957 Spevack et al 252-392 2,945,821 7/ 1960 Sterlin 252-392 3,034,907 5/ 1962 Kleeman et al. 252-392 X 3,116,252 12/1963 Beretvas 252-392 X 3,119,447 1/ 1964 Raifsnider et al. 252-389 X 3,201,411 8/ 1965 Freedman 252-855 LEON D. ROSDOL, Prz'mdry Examiner.

SAMUEL H. BLECH, Examiner.

M. WEINBLA'IT, Assistant Examiner. 

1. A CORROSION INHIBITING COMPOSITION CONSISTING OF THE FOLLOWING THREE COMPONENTS: (1) ABOUT 0.5 PART BY WEIGHT OF AN ACYL DERIVATIVE OF N-ALKYL AMINO ACETIC ACID OF THE FORMULA: 